Excerpts of these diseases have been reprinted with permission from the APHA’s Control of Communicable Diseases Manual (CCDM). Please refer to the CCDM for complete information about each disease.
SEVERE ACUTE RESPIRATORY SYNDROME ICD-10 U04.9 (provisional)
1. Identification – A severe respiratory infection with associated gastrointestinal manifestations in an as yet unknown percentage of those infected, Severe Acute Respiratory Syndrome (SARS) was first recognized in February 2003. The causal agent is a coronavirus. The disease is thought to have originated in the Guandong Province of China, with emergence into human populations sometime in November 2002. By July 2003, major outbreaks had occurred at 6 sites: Canada, China (originating in Guangdong Province and spreading to major cities in other areas, including Taiwan and the Special Administrative Region of Hong Kong), Singapore and Viet Nam. The disease spread to more than 20 additional sites throughout the world, following major airline routes. The major part of the spread occurred in hospitals and among families and contacts of hospital workers. SARS presents with malaise, myalgia and fever, quickly followed by respiratory symptoms including cough and shortness of breath. Diarrhea may occur. Symptoms may worsen for several days coinciding with maximum viraemia at 10 days after onset. Laboratories performing SARS-specific PCR tests must adopt strict criteria to confirm positive results, especially in low prevalence areas, where positive predictive value will be lower. Diagnostic tests include PCR, ELISA and IFA. A confirmed positive PCR for SARS requires at least 2 different clinical specimens (e.g. nasopharyngeal and stool), or the same clinical specimen collected on 2 or more days during illness (e.g. 2 or more nasopharyngeal aspirates), or 2 different assays, or repeat PCR using a new extract from the original clinical sample on each occasion of testing … The PCR procedure must include appropriate negative and positive controls in each run. A positive PCR result must be confirmed by repeat PCR using the original sample, or testing the same sample in another laboratory … Virus isolation is done by cell culture of SARS-CoV from any specimen, plus PCR confirmation using a validated method. In the post-outbreak period, all sporadic cases and clusters should be independently tested at another SARS reference laboratory with validated methods. As of 1 October 2003 WHO surveillance case definitions include definitions for both a suspect and a probable case … A suspect case is a person presenting after 1 November 2002 with a history of: high fever (>3g°C/100.4°F) and cough or breathing difficulty and one or more of the following exposures during the 10 days prior to onset of symptoms: close contact (caring for, living with or in direct contact with respiratory secretions or body fluids) with a suspect or probable case of SARS; history of travel to an area with recent local transmission of SARS; current residency in an area with recent local transmission of SARS. A person with an unexplained acute respiratory illness resulting in death after 1 November 2002 on whom no autopsy has been performed is also considered a suspect case if one or more of the following occurred during the 10 days prior to symptoms onset: close contact with a suspect or probable case of SARS, history of travel to an area with recent local SARS transmission, residence in an area with recent local transmission of SARS at the time of death. A probable case is a suspect case with X-ray evidence of infiltrates consistent with pneumonia or respiratory distress syndrome (RDS), or positive for SARS coronavirus by one or more assays, or presenting autopsy findings consistent with RDS without identifiable cause. A case should be excluded from surveillance if an alternative diagnosis can fully explain the illness as more diagnostic tests continue to be performed and the disease evolves. Because SARS is currently a diagnosis of exclusion, the status of a reported case may change over time … The clinical spectrum and course of SARS vary and appear to depend on immunological factors as yet not fully understood. From a review of probable cases, dyspnoea sometimes rapidly progresses to respiratory failure requiring ventilation; about 89% of cases recover and the case fatality rate is about 11%. From data collected during outbreaks, the likelihood of death from SARS appears to depend on characteristics of those infected, including age and presence of underlying disease. Current understanding, based on limited numbers of patients, suggests that the case fatality is less than 1% in persons aged 24 years or younger, 6% in persons aged 25 to 44 years, 15% in persons aged 45 to 64 years, and above 50% in persons aged 65 years or more.
2. Infectious agent – SARS is caused by a coronavirus similar, on electron microscopy, to animal coronaviruses. It is stable in feces and urine at room temperature for at least 1-2 days, and for up to 4 days in stools from patients who manifest diarrhea. The SARS virus loses infectivity after exposure to different commonly used disinfectants and fixatives …
3. Occurrence – Major outbreaks of SARS occurred during the period November 2002 to July 2003 in Canada, China (including Hong Kong Special Administrative Region and Taiwan), Singapore and Viet Nam. The virus is known to have been transported by infected humans to over 20 additional sites in Africa, the Americas, Asia, Australia, Europe, the Middle East and the Pacific. On July 5, 2003 WHO reported that person-to-person transmission of the SARS virus had been interrupted at all outbreak sites and recommended that intensified surveillance be continued to determine whether or not the disease had become endemic and would reappear … An isolated event in which a laboratory worker became PCR positive for the SARS virus occurred in Singapore in early September 2003. A similar isolated laboratory worker infection occurred 3 months later in Taipei (Taiwan, China), without secondary transmission. A third laboratory infection involving 2 workers occurred in Beijing in April 2004. One of the cases transmitted the infection to a family member and a health worker, which resulted in a small third generation outbreak and full containment activities by the Chinese health authorities.
4. Reservoir – Unknown. Initial studies in Guandong Province, China, showed similar coronaviruses in some animal species sold in markets and further study continues.
5. Mode of transmission – SARS is transmitted from person to person by close contact … This is thought to be primarily spread via droplets and possibly fomites. In one instance, the virus is thought to have been transmitted from person to person through some environmental vehicle …
6. Incubation period – From 3 to 10 days.
7. Period of communicability – Not yet completely understood. Initial studies suggest that transmission does not occur before onset of clinical signs and symptoms, and that maximum period of communicability is less than 21 days …
8. Susceptibility - Unknown but assumed to be universal …
9. Methods of control
A. Preventive measures:
1) Identify all suspect and probable cases using the WHO case definitions:
Persons who arrive at health care facilities and require SARS assessment must be rapidly diverted by triage nurses to a separate area …. and be given a face mask, preferably one that provides filtration of expired air. Health workers involved in the triage process should wear a face mask … with eye protection, and wash hands before and after contact with any patient, after activities likely to cause contamination and after removing gloves …
2) Isolation of probable cases:
Probable SARS cases should be isolated and accommodated as follows in descending order of preference: negative pressure rooms with door closed, single room with own bathroom facilities, cohort placement in an area with an independent air supply, exhaust system and bathroom facilities. If an independent air supply is not feasible, air conditioning should be turned off and windows opened (if away from public places) for good ventilation.
Strict universal precautions for infection control must be practised using precautions for airborne, droplet and contact transmission … Disposable equipment should be used wherever possible in treatment and care of patients with SARS, and disposed of appropriately. If devices are to be reused, they must be sterilized according to manufacturers' instructions … Handwashing is crucial and access to clean water essential … Alcohol-based skin disinfectants can be used if there is no obvious organic material contamination … patients' linen must be prepared on site for the laundry staff and placed into biohazard bags.
3) Contract tracing: For all persons fitting the suspect or probable case definition for SARS ...
B. Control of patients contacts and the immediate environment:
1) Patient management:
Hospitalize under isolation or cohort with other suspect or probable SARS cases, keeping the 2 categories of patients separated. Obtain samples (sputum, blood, serum and urine,) to exclude standard causes of pneumonia (including atypical causes); consider possibility of coinfection with SARS and take appropriate chest radiographs … Use full personal protection equipment for collection of specimens and for treatment/interventions that may cause aerosolization … At the time of admission, prescription of antibiotics for the treatment of community-acquired pneumonia is recommended until diagnoses of treatable causes of RDS have been excluded. Numerous antibiotherapies have been tried for treatment of SARS with no clear effect. Ribavirin with or without use of steroids has been used in several patients, but its effectiveness has not been proven and there has been a high incidence of severe adverse reactions …
2) Contact management:
Give information on the signs and symptoms and means of transmission to each contact.
Place under active surveillance for 10 days and recommend voluntary isolation at home and record temperature daily, stressing to the contact that the most consistent first symptom that is likely to appear is fever. Ensure contact is visited or telephoned daily by a member of the public health care team to determine whether fever or other signs and symptoms are developing. If the contact develops fever or other SARS signs and symptoms, follow up examination should be done at an appropriate health care facility. If the suspect or probable SARS case has been removed from surveillance because an alternative diagnosis can fully explain the illness, contacts can also be removed from surveillance and discharged from follow up.
C. Epidemic Measures:
During the SARS outbreaks of 2003 the perception of risk of infection by the general population was far greater than the actual risk of infection. Epidemic measures therefore should clearly inform the general public … Ensure adequate triage facilities and clearly indicate to the general public where they are located and how they can be accessed.
D. Disaster Implications:
As with other emerging infections, severe adverse economic impact and socio-economic consequences have been shown to occur.
E. International Measures:
WHO maintains global surveillance for clinically apparent cases of SARS (probable and suspect cases) … A global response facilitating the work and exchange of information among scientists, clinicians and public health experts has been shown to be effective in providing information and effective evidence-based policies and strategies.